1. Field of the Invention
The present invention relates to an abnormality diagnosis apparatus and to a method for an electric pump which supplies a working fluid to, for example, a driving system of a vehicle.
2. Description of the Related Art
With regard to this type of an electric pump, in a technique disclosed in, for example, Japanese Laid-open (Kokai) Patent Application Publication No. 2006-25493, protection control for limiting a current value with respect to a pump driving motor is performed based on a component temperature and a continuous operation time so as to prevent an abnormality caused by heat generation.
According to the disclosure of Japanese Laid-open (Kokai) Patent Application Publication No. 2006-25493, the electric pump is controlled such that an actual number of rotations tracks a commanded value of the number of rotations (the target number of rotations) of the pump driving motor given from an external device irrespectively of a state of the pump side. Therefore, in some cases, the actual number of rotations cannot track the commanded value by way of the protection control.
However, conventionally, according to abnormality diagnosis of the electric pump of this type, it is decided whether or not an abnormality occurs based on tracking (deviation) of the actual number of rotations with respect to the commanded value, and therefore, even if the electric pump is functioning normally, there is a probability that erroneous decision that an abnormality occurs is made.
Furthermore, when an extremely high commanded value is given due to, for example, an abnormality to generate a commanded value or a communication abnormality between the external device and the electric pump (motor driving circuit), the actual number of motor rotations cannot track the commanded value, and thus, in the same way as the above, even if the electric pump is functioning normally, there is a probability that an erroneous decision that an abnormality occurs will be made.